With the development of network technologies, a network architecture featuring forwarding and control element separation emerges, for example, OpenFlow (OpenFlow).
A network with the network architecture featuring forwarding and control element separation includes two types of network devices: a forwarding plane apparatus and a control plane apparatus. The forwarding plane apparatus processes received packets according to a flow table. The control plane apparatus manages the forwarding plane apparatus by using a control channel.
“Forwarding and control element separation” means that the forwarding plane apparatus is separated from the control plane apparatus. The forwarding plane apparatus transfers partial or all control plane functions to the control plane apparatus. The forwarding plane apparatus has the capability of communicating with the control plane apparatus. The forwarding plane apparatus is capable of communicating with the control plane apparatus by using a control channel.
When the control plane apparatus is faulty or a link between the control plane apparatus and the forwarding plane apparatus fails, the control plane apparatus is incapable of managing the forwarding plane apparatus. When the control plane apparatus is incapable of managing the forwarding plane apparatus, the forwarding plane apparatus needs to actively obtain information used for packet forwarding path calculation. As a result, the forwarding plane apparatus needs to actively obtain the information used for packet forwarding path calculation before calculating a packet forwarding path based on the information used for packet forwarding path calculation.